1. Field of the Invention
The present invention relates to a semiconductor device wherein electrode pads on a semiconductor chip are electrically connected to lead terminals by, e.g., plating bonding and a method for manufacturing the same and, more specifically, to a semiconductor device having a face-down-mounting (face-down-bonding) structure and a method for manufacturing the semi-conductor device by the plating bonding.
2. Description of the Related Art
Plating bonding using metal plating has recently been employed experimentally in order to electrically connect electrode pads on the surface of a semiconductor chip and inner leads of lead frames. In this plating bonding, the electrode pads and inner leads are aligned with each other and then soaked in a solution of electrolytic plating thereby to form a metal plating layer at each of connecting portions of the pads and leads.
FIG. 1 is a cross-sectional view schematically showing a semiconductor packaging device as an example of a semiconductor device manufactured by the plating bonding described above. In the semiconductor packaging device, the proximal ends of inner leads 3a of lead frames 3 are bonded onto the surface of a semiconductor chip 1 using an adhesive tape 2. Since a metal plating layer 4 is formed between an electrode pad 1a and a projection 3a' of the distal end of each of the inner leads 3a to electrically connect the pad and inner lead, an LOC (Lead-On-Chip) structure can be achieved. The periphery of the chip 1, including the above connecting portions, i.e., metal plating layers 4, is sealed with resin 5, and outer leads 3b of the lead frames 3 are formed into a predetermined shape. The semiconductor packaging device having such a structure has the advantage that it can be made considerably thinner than a device wherein electrode pads on a semiconductor chip and inner leads of lead frames are connected by wiring.
In the semiconductor packaging device shown in FIG. 1, when the projections 3a' of inner leads 3a and the electrode pads 1a contact each other, i.e., when they are in an initial contact state, the metal plating layers 4 grow sufficiently. In other words, in the initial contact state, plating is obtained from both the inner leads 3a and electrode pads 1a at the same time. Therefore, the metal plating layers 4 formed between the electrode pads 1 and inner leads 3a permit stable, efficient plating bonding.
However, in the prior art semiconductor packaging device described above, it is difficult to bring the projections 3a' of all the inner leads 3a into reliable contact with the electrode pads 1a since the inner leads 3a vary in height. If the inner leads 3a and electrode pads la do not contact reliably, the metal plating layers 4 cannot be grown sufficiently and thus the plating bonding is deteriorated in reliability.